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Feathers found on ostrich-like dinosaur in Alberta

University of Alberta researcher’s study of a 75-million-year-old fossil finds clear evidence of individual feathers and a patch of skin

An artistic reconstruction of the feathered ornithomimid dinosaurs found in Alberta. (Julius Csotonyi photo)

By Bob WeberThe Canadian Press

Thu., Oct. 29, 2015

EDMONTON — A University of Alberta dinosaur researcher was just looking for a project when he chose one fossil specimen out of others still lying around unexamined from a six-year-old dig.

But when Aaron van der Reest cracked the plaster shell protecting the 75-million-year-old specimen from southern Alberta, he got a lot more than that.

“My first thought was, ‘Is this actually what I think it is?’”

Van der Reest was studying ornithomimus, a dinosaur that looked very much like an ostrich. What he found on bones connecting the leg to the breast was something never seen before on a North American fossil — feathers.

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“They look like little tiny black lines,” said the undergraduate in paleontology, who describes his find in a journal paper published Wednesday. “The thickest is about a half-millimetre across.”

Feathered dinos have been found before but most come from China. Not only is van der Reest’s sample believed to be a North American first, it’s one of the best-preserved in the world and includes a patch of skin.

“We can see individual feathers,” he said Wednesday, still sounding slightly in awe despite the two years it took him to clean and prepare the specimen.

The fossil reveals what ornithomimus’s tail plumage was like. Scientists are still studying molecules within the feathers to see if they hint at colour, but van der Reest can say they would have been fluffy, without the tiny hooks that hold the branches of modern feathers together.

As for the skin, it seems to have been mostly smooth with pores for feathers. It may have looked much like a plucked goose, he said.

The dinosaur would have looked so much like an ostrich, van der Reest theorizes ornithomimus used a combination of feathers and bare skin for the same reason today’s birds do — to regulate heat.

“It’s virtually identical,” he said. “Chances are ornithomimus is doing exactly the same thing (as ostriches).”

The correspondences are so strong van der Reest believes that they don’t just apply to his object of study.

“There’s a really good chance that other dinosaurs are doing the same thing,” he said.

Three years ago, a paleontologist at the University of Calgary studying ornithomimus fossils offered the theory that the “wing-like structures” found on ornithomimus fossils held feathers for preening, not flight.

“They may have initially evolved as a secondary sexual characteristic,” Darla Zelenitsky said in a paper published in 2012 in the prestigious journal Science.

“These wing-like structures would have been used for reproductive activities (courtship, display, brooding) and were only later ... co-opted for other roles including flight.”

The fossils, found in 2008 and 2009, have pushed back the date of the earliest fossil feather by about 10 million years. As well, they were the first feathered dinosaur fossils found in North America and the first found in relatively coarse sandstone.

But things got even more interesting when Zelenitsky compared the two fossils with a third adult ornithomimus unearthed in the same area in 1995. Despite being from exactly the same species, this dinosaur had much more advanced feathers.

“Their distribution and orientation are similar to the insertion pattern of covert feathers, which form the bulk of the feather covering in modern bird wings.”

At about 150 kilograms, Ornithomimus was too big to fly, says Zelenitsky. And the fossils also suggested that real feathers weren’t something Ornithomimus grew until it was fully adult.

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